A cleaning device configured to use an adhesive roller and utilize its adhesive force so as to remove foreign matter such as dust adhering onto a surface of a thin member to be cleaned such as a glass substrate for a flat panel display (FPD), a printed board, or a bonded film has been conventionally known as a cleaning device for removing the foreign matter.
Such an adhesive roller cannot remove minute foreign matter (such as foreign matter having an average diameter of 1 μm or less). Moreover, it is difficult to completely remove foreign matter such as dust that has once adhered onto a surface of the adhesive roller (an adhesive layer), thereby degrading maintenance performance. Additionally, since the adhesive roller is pressed against a member to be cleaned under a certain pressure so as to remove the foreign matter, when the member to be cleaned is, for example, a film, there is a fear that not only the foreign matter but also the film is possibly stuck onto the surface of the roller.
In view of the above, the applicant filed another patent application based on the findings that in removing foreign matter such as dust from a member to be cleaned by using electrophotography, electric charges capable of electrostatically adsorbing the foreign matter are electrically charged onto a surface of a cleaning roller by peeling charging (or contact charging), so that the foreign matter can be removed by the cleaning roller by utilizing the electrostatic force (refer to Japanese Patent Application No. 2008-271797).
The foreign matter is sequentially accumulated on the surface of the above-described cleaning roller, and therefore, maintenance work need be periodically performed to remove the foreign matter from the surface of the cleaning roller. Hence, the applicant had filed before patent applications about a cleaning system provided with a transfer roller or a charging control roller with respect to the cleaning roller so as to stably continue adsorbing and removing operations for the foreign matter by the cleaning roller for a long period of time without periodically performing such maintenance work (refer to Japanese Patent Application Nos. 2009-069972, 2009-138107, and 2009-138108).
The cleaning systems according to the patent applications are provided with a cleaning brush, a metallic roller, a cleaning blade, and the like, so as to remove foreign matter adsorbed onto the transfer roller and maintain the function of the transfer roller for a long period of time.